Hydroprocessing processes have been used to improve poor quality petroleum derived feeds for catalytic cracking reactions. For example, hydrotreating processes have been used to improve resids, vacuum gas oils, coker gas oils, middle distillates and recycle streams from the fluid catalytic cracking (FCC) unit. These processes generally use a catalyst to remove nitrogen and/or sulfur and to at least partially hydrogenate multi-ring aromatics or naphtheno-aromatics to hydrogen enriched naphtheno-aromatics and naphthenes which are more easily cracked in the FCC unit with less coke and tar make.
It is known that heavy hydrocarbonaceous fractions of petroleum can be more effectively hydrotreated if mild hydrocracking also takes place in the hydrotreating reactor. Physical mixtures of catalysts are known to impart separate cracking functionality and hydrogenation functionality. In theory, (a) mild cracking would open naphthene rings which would not dehydrogenate and revert back to the aromatic structure and (b) the multi-ring aromatics or naphtheno-aromatics would be hydrogenated to render them more easily cracked in FCC with less coke and tar make. Unfortunately, these dual catalyst systems have not proven to be commercially feasible because the catalysts which promote cracking activity, such as zeolite-containing catalysts and other solids with acidic sites, deactivate rapidly due to the presence of basic nitrogen and other impurities present in the hydrotreating reactor.
It is therefore an object of the invention to provide a hydroprocessing process utilizing a dual catalyst system including a hydroprocessing catalyst and a second catalyst which enhances the performance of the hydroprocessing catalyst. It is a further object of the invention to provide a hydroprocessing process utilizing a hydroprocessing reactor containing a dual catalyst system including a hydroprocessing catalyst and a second catalyst which enhances the performance of the hydroprocessing catalyst wherein the second catalyst is not materially deactivated in the hydroprocessing reactor.